The following invention relates to what is commonly known as an infinity display, a class of viewing device that is capable of displaying images or scenes as if they were set at or approaching, “infinity focus”.
Such displays are commonly used in aircraft flight simulators recreating aerial vistas at optical infinity, offering the trainee pilot a highly credible panorama. However, the optical components that constitute the prior art tend to be large and very expensive, hence infinity displays tend to be restricted to applications where space is not a significant issue and price gives way to necessity. Furthermore, unlike the present invention, such infinity displays do not offer autostereoscopic views and motion parallax.
The prior art essentially requires that a single image undergoes magnification, where all point sources emanating from the display screen e.g. a CRT or LCD are enlarged to the extent that their light rays become or approach, collimation. This creates the illusion of depth as all virtual images appear deeper than their corresponding point source and as magnification increases so the image recedes into the distance.
However, non-paraxial (i.e. non-centred) rays are subject to distortion. To minimise chromatic distortion and other optical aberrations, heavy compound lenses are frequently used especially in the case of large simulator displays, coupled with beam-splitters and sizeable first surface mirrors. Even then, the resulting anastigmatic system provides a relatively narrow angular view as the objective lens is limited in its ability to accurately focus non-paraxial rays that emerge from the periphery of the SLM.
The aforementioned reduced breadth of view together with the prior art's size and cost prohibit it from being used in many other applications that could potentially benefit from the technology.
HinesLab Inc., have developed a Cylindrical Catadiotropic Infinity Display (CCID) that employs thin section, astigmatic lenses, beam splitters and polarisers to reduce the weight and size of the system. Although a clever arrangement offering a broader angular view, the depth of the optical arrangement (stacked optics) likely restricts or precludes its use in many applications such as to be found in the entertainment industry, advertising and quite significantly, the domestic sector.
The above problem is addressed in WO 2005/124428 filed by Dr Amitai Yaakov by offering spectacles that like many helmet mounted systems today, use total internal reflection to bounce an image within a transparent light guide toward a reflective interface. This allows the image to break out or “uncouple” from the light guide whilst simultaneously directing it toward the wearer's eye. In the case of WO 2005/124428, the reflective interface is a stack of partially reflective surfaces that are angled toward the wearer. These systems are ideal for “beaming” images into a recipient's eye but are not designed for, nor lend themselves to, large multi-viewer displays for several reasons. First, the reflective surfaces incorporated into the light guide would make it expensive and difficult to fabricate if scaled up to the dimensions of a conventional flat screen display. Secondly, said juxtaposed partially reflective surfaces will begin to impinge or separate from one another as you move your head from side to side, creating unwelcome image artefacts.
Other infinity display technologies are intended for use in “head up displays” (HUD's).
U.S. Pat. Nos. 1,538,545; 4,711,512 and 5,076,664 relate to HUDs that use light guides and uncoupling optics to present a collimated image to a pilot's eye(s). However, each of these is clearly limited in terms of their display width as they are designed to collimate a SLM's image using centrally stacked collimating lenses comparable in width to the display's entrance pupil, thus a wide screen would necessitate a wide objective (or centrally stacked lenses) situated at a commensurately distant focal point. As in WO2005/124428 above, the issue of display width is not directly addressed, probably because it is not a requirement, such devices being geared specifically to the visual field of a single user.
High specification, large, multi-viewer infinity displays in existence today would appear to be at best of comparable size to the HinesLab CCID which, as mentioned earlier, is ideal for cockpit scene simulation but is arguably not thin enough in profile to satisfy the full breadth of many potential applications.
Indeed, the adoption of thin profile infinity display systems by the domestic sector would turn it from an abstruse technology to an every day, broad application, visual display device, most likely in the form of a “deep-view TV” and/or an “infinity window”. The latter would effectively render a scene e.g. a rural landscape as if it were at infinity focus, creating the illusion of a “real scene” existing beyond the display as if one were looking through an actual window.
Other applications abound. A thin profile or to use today's nomenclature “flat-screen” infinity display, would enhance the immersive experience of high-end arcade machines, proprietary game consoles and other entertainment oriented systems that rely on taking the user one step closer to “reality”, by offering a convincing simulation. If autostereoscopic images were included, then the visual experience would be even more exciting.